Abstract: Saturated steam is an important working medium for steam turbines. The wetness of the steam will directly affect the safe and economic operation of steam turbines. Therefore, it is of great significance to realize the reliable on-line measurement of the steam wetness. In order to verify the feasibility of two-phase flow wetness measurement technology based on ultrasonic sound velocity method, this paper firstly introduces some necessary assumptions, and proposes a theoretical model of wetness measurement by sound velocity method. Theoretical analysis shows that the medium wetness is the function of sound velocity, temperature and pressure. The function of direct variables has fewer direct measurement variables, and the overall structure of the model is relatively simple. On this basis, the cold-state experimental study is carried out with air-droplet as the object to further verify the feasibility of the model. The experimental results show that with the increase of wetness, the sound velocity of the medium gradually decreases, and the two have a strong linear relationship. In the wetness range of 0~20%, the speed of sound change is about 22 m/s. The two-phase flow wetness measurement scheme based on the ultrasonic sound velocity method is with certain feasibility.